Technical data

Functional description
91
DHW tank temperature control (continued)
Control sequence
DHW tank temperature falls
(Set-point value –2.5 °C / 4.5 °F,
selectable via coding address ”59”)
The desired boiler water temperature
is set 20 K higher than the DHW
temperature set-point value (selectable
via coding address ”60”).
The circulation pump for heating the
DHW tank is switched on immediately
(Coding ”61: 01”).
Boiler temperature-dependent switching
of the circulation pump for heating the
DHW tank (Coding ”61: 00”):
The circulation pump is switched on
when the boiler water temperature is
7°C / 13°F higher than the domestic
hot water temperature.
With priority control:
(Coding ”A2: 2”)
The supply temperature set-point
value is set to 0 °C / 32°F when the
DHW tank is being heated. The
mixing valve is closed and the
heating circuit pump is switched off.
Without priority control:
The heating circuit control continues
to operate as normal with the
setpoint value unchanged.
With modulating priority control (only
in conjunction with mixing valve
circuit):
The heating circuit pump remains
switched on. The desired supply
temperature is lowered as long as the
desired boiler water temperature is
not reached while the DHW tank is
being heated. The desired supply
temperature is dependent on the
difference between the desired and
the current boiler water temperature,
the outdoor temperature, the heating
curve slope and the setting of the
coding address ”A2”.
DHW tank temperature rises
(Set-point value +2.5 / 4.5°F)
The boiler water temperature set-point
value is reset to the weather-
compensated value.
When the DHW tank has been
heated up, the circulation pump for
heating the DHW tank continues to
run until:
the temperature difference between
the boiler water and domestic hot
water is less than 7°C / 13°F, or
the desired, weather-compensated
boiler water temperature is
reached, or
the desired domestic hot water
temperature is exceeded by
5°C / 9 °F.
The max. run-on time is 15 minutes
(selectable via coding address ”62”).
Circulation pump for heating the
DHW tank without run-on time
(Coding ”62: 00”):
The circulation pump is switched off
immediately.
With priority control
(Coding ”A2: 2”):
The supply temperature set-point
value is reset to the weather-
compensated value.
The heating circuit pump is
switched on.
With optimized DHW tank heating
(Coding ”55: 1”):
Optimized DHW tank heating takes
into account the rate at which the
temperature increases during
domestic hot water heating.
It also takes into account whether
the boiler must supply heat for space
heating purposes after heating up the
DHW tank or whether the residual
heat of the boiler should be
transferred to the domestic hot
water DHW tank.
The control unit determines the
switch-off time of the burner and the
circulation pump accordingly so that
the desired domestic hot water
temperature is not substantially
exceeded after DHW tank heating is
completed.
5285 941 v.1.5